The field of restorative dentistry using artificial roots in the presently preferred form of osseointegrated cylinder shaped dental implants has progressed to the level where attention is now being given to providing restorations on them that closely replicate natural dentition in appearance, especially where the teeth emerge from the gums. The problems of achieving a natural locking emergence profile are addressed using a technique for fabricating implant supported restorations directly to an implant, employing custom wax patterns fashioned on abutment cylinders to achieve, for example, a custom made porcelain fused to metal restoration. This technique is described in published articles that appeared in The International Journal of Oral and Maxillofacial Implants, Vol. 3, Number 1, 1988 at pages 25-26 xe2x80x9cSingle Tooth Implant Supported Restorationsxe2x80x9d Lewis, S. G. et al., and Number 3, 1988 at pages 183-189 xe2x80x9cThe xe2x80x98UCLAxe2x80x99 Abutmentxe2x80x9d, Lewis, S. G. et al. A similar result using a different abutment is described in U.S. Pat. No. 4,988,298, which is owned by the Assignee of the present invention. The problem is incompletely addressed in U.S. Pat. No. 5,073,111 issued to Daftary Dec. 17, 1991.
The dental restoration of a wholly or partially edentulous patient with dentition supported on dental implants is now frequently done in two stages. In the first stage the implant is placed and left to integrate with the jawbone. The second stage begins with re-accessing the implant through the gum and maintaining access with a healing cap or the like, and continues through the fabrication of restorative dentition in the laboratory using measurements and other information taken from time to time from the patient. During that time the patient may have only a healing cap is his or her mouth, or according to more recent and sophisticated procedures the patient may be fitted with temporary dentition from which additional refining measurements can be taken. Nevertheless, the healing abutments and the transfer copings, or pick up copings, of the prior art do not cooperate to provide room for making and installing on the implant an artificial tooth having an aesthetically pleasing or anatomically correct emergence profile. The gingival aspect of an implant is, typically not more than about 4.1 mm in diameter, whereas the longer (mesial-distal) dimension of a natural tooth where it emerges from the gum is between about 4.5 mm and about 8.0 mm. According to present practice, healing abutments, which are cylindrical in cross section, are chosen to approximate the mesial-distal dimension of the tooth being replaced. At the same time, the transfer copings, or pick up copings, of the prior art are all one size, about 4.5 mm in diameter. As a result, a gap is left in the gingiva, around the coping, and impression material fills this gap when an impression is taken. The gingiva also tend to collapse into this gap, resulting in less than accurate replication of the conditions in the patient""s mouth. As a further consequence of these problems, it is difficult to make soft tissue models accurately. Stone models replicate these errors, and this requires technicians to shape the stone manually to comply with the conditions in the patient""s mouth, or risk producing a crown with an inaccurate emergence profile or crown to abutment margin that is misplaced. These are severe problems, resulting from the fact that the designers of prior art components have thus far failed to recognize them. The present invention teaches new surgical and laboratory components, and new procedures, which eliminate such inaccurate and time wasting procedures, and improve the art of making anatomically correct and aesthetically pleasing dental restoration.
In accordance with the present invention, a healing cap or healing abutment sized to maintain space for a desired emergence profile through the gum is used at the beginning of the second stage, in combination with an impression coping, or a pick up coping, having similar size specifications so that when the impression coping is fitted to the implant for taking the impression from which the stone model will be made the space for the desired emergence profile established in the gum by the healing abutment, or cap, will be preserved and replicated in the stone model, and in a soft tissue model, if desired. From such models restorative dentition can be fabricated without requiring the use of a specially contoured tooth support abutment as taught by Daftary, for example. Rather, artificial teeth replicating in all material respects the natural teeth that they replace can be fashioned on the model using components that have become standard in the art.
In one of its aspects the invention teaches a new method of preparing an aesthetically pleasing, as well as anatomically correct dental restoration on a natural or artificial root comprising first the step of preparing in the gingiva overlying the root an opening to the gingival aspect of the root, which opening is sufficient to accommodate the shape and contour of a natural tooth emerging through the gingiva from the root, followed by the step of making a rigid (e.g., stone) model that reproduces in stone or in overlying soft tissue exactly that opening and gingival aspect of the root, and then the step of forming on the model an artificial tooth that replicates in that opening the shape, size and contours desired in the restoration, and finally installing that restoration on the root. In another aspect, the invention provides a healing member (sometimes called a cap) that has a transmucosal section having at one end the subgingival cross sectional size and shape of the artificial root and where it emerges from the gingiva the mesial-distal size of the natural tooth being replaced, and means to attach that healing member non-rotatively to the root, for establishing the above mentioned opening in the gingiva. In another aspect, the invention provides a transfer coping for use in making the above mentioned rigid model having a transmucosal section that is substantially identical in cross sectioned size and shape to the transmucosal section of the healing member so as to fit fully within the opening in the gingiva that was formed by the healing member, and a supragingival section shaped for non-rotational embedment in resilient modelling material, together with means to attach the coping non-rotatively to the root. In still another aspect, the invention provides sets of matched pairs of healing members and transfer copings shaped and sized for use according to the invention to prepare restorations of particular types of teeth, such as molars, premolars, bicuspids, and incisors, as examples.